It is well known to provide a vehicle with any number of air treating systems to purify cabin air. In U.S. Pat. No. 5,667,560 to Dunne, a faujasite having a specific zeolite structure is coated on a rotating heat wheel. Cabin air is passed through a wheel portion whereat VOC's (volatile organic compounds) are adsorbed and the spent cabin air dehumidified whereupon it is returned as conditioned air to the cabin. The wheel rotates to another station where the adsorbed VOC's are heated and released to the atmosphere. Generally, cabin air treating systems are not entirely dissimilar to and bear resemblance to HVAC systems used in stationary buildings and the like. The cabin has a set volume of air which can be exhausted, purified and returned in relatively small sized units which can be easily mounted as appendages onto the vehicle.
It is well known that a large volume of atmosphere is drawn in when a motor vehicle operates. In German patent DE 43 18 738C1, published Jul. 14, 1994, it is noted that 384,000 m3 of purified air could be possible within an hour of operation of 1,000 motor vehicles. The German patent does not describe how this is possible except by some general statements. However, long before the German patent, it was known to use the vehicle, itself, as a mobile atmosphere cleansing device. An air duct positioned on the vehicle and equipped with filters (electronic precipitators) for cleaning the air is disclosed in U.S. Pat. No. 3,738,088 to Colosimo. Colosimo mentions that a portion of the filtered air can be directed into the vehicle's carburetor. Colosimo also mentions that a catalytic postfilter, such as of the replaceable cartridge type, can be positioned downstream of the electrostatic precipitators to filter hydrocarbons (HC), nitrous oxides, sulphur oxides and the like. Obviously Colosimo's postfilter must adsorb or absorb VOC's until it is saturated whereupon it is replaced.
The assignee's related PCT publications WO 96/22146 and WO 97/11769 are directed to vehicular atmosphere cleansing devices and disclose catalytic compositions for removing i) ozone or ii) ozone and CO or iii) ozone, CO and HC's from an air stream, preferably passing through the vehicle's radiator on which is coated the catalytic compositions, as defined in the publications. The cleansed air is returned to atmosphere. The references are principally directed to catalyst compositions found effective to remove ozone, per se, or provide oxidation capabilities to not only remove ozone but also oxidize pollutants from atmospheric air at ambient temperatures contacting vehicular surfaces at vehicle operating temperatures. However, both references also mention as an alternate embodiment a pollutant treating catalyst composition which may comprise an activated carbon composition that can catalyze reduction of ozone to oxygen as well as adsorb other pollutants. The publications also suggest the used of adsorbent compositions to adsorb hydrocarbon (HC) and/or particulate material for later oxidation or subsequent removal and mentions zeolites, other molecular sieves, carbon and Group IIA alkaline earth metal oxides as adsorbers. No discussion of how the later oxidation or subsequent removal is accomplished in an automotive environment or even if regeneration is to be employed is made in the cited publications.
In a co-pending application, U.S. Ser. No. 09/460,924, filed Dec. 24, 1999 (US00/33061), there is disclosed a 2 stage zeolite trap arrangement which is sized to sequentially trap “large” HC's and then “smaller” HC's. Mixed with the zeolite is an oxidation catalyst, preferably selected from the platinum group metals. In the automotive application discussed in this application, a heated stream is valved into contact with the zeolite to affect desorption or a rotating heat wheel with an external heating source is disclosed. In either arrangement, because the platinum group metal catalyst oxidizes the VOC's, the air is cleansed after leaving the catalyst and exhausted to atmosphere. While this is an effective arrangement, the expense of the platinum group metal catalyst increases the system cost.
In another co-pending application, U.S. Ser. No. 09/391,637, filed Sep. 7, 1999 (US00/24343), there is disclosed a switching arrangement for a VOC adsorber/desorber especially adapted for automotive applications. The adsorber is described generally by reference to the above PCT applications to include such agents as zeolite, cordierite, active carbon, mullite or silicone carbide. The desorption is accomplished by switching in several disclosed ways. In one method, an electrical resistance heater is periodically heated. In another way, the outlet of the ambient air being drawn into the engine is blocked by valved passages maintained at different temperatures or by air directing louvers. The VOC's recovered during the desorption switch are directed into the engine's intake manifold and subsequently cleansed by the vehicle's catalytic converter exhaust system. In the adsorption stage the cleansed air can be emitted to atmosphere and a stream siphoned off to the intake manifold. The engine's ECU A/F ratio is said to be programmed to account for the periodic desorption stage and possibly control the switch between the stages. While a number of arrangements are disclosed in the prior application, it is generally not desirable in a vehicular environment to effect switching an ambient air stream which has an automotive cooling function nor is it desirable, from a reliability standpoint, to have moving parts that switch air streams or even periodically shut off and on the air streams. This prior application also mentions that conceptually an adsorbing wheel, a moving adsorbing strip or belt, etc in which the adsorbent means are located on or consist of a movable element can be utilized but no further discussion or showing of any such moving arrangement is disclosed. In general, the subject invention is directed to an adsorber/desorber arrangement for vehicular cleaning of the atmosphere, which avoids the expense of an oxidizing catalyst. It also addresses the problem of VOC disposal when the adsorber is regenerated by transferring the desorbed VOC's to the engine where the engine combustion and/or catalytic converter on the vehicle can oxidize the emissions. It is believed that the fundamental approach set forth in this application represents the type of system that can be viably commercialized. Accordingly, the invention in this application may be viewed as an extension, refinement or improvement of the basic concepts disclosed in the invention of U.S. Ser. No. 09/391,637.
Within the emission control art for treating exhaust emissions from vehicles powered by internal combustion engines, it is well known to provide a light-off catalyst in the exhaust system near the exhaust manifold which traps hydrocarbons (HC) during start-up of the vehicle and releases the HC for subsequent conversion by the vehicle's catalytic converter when the engine warms up. These light-off catalysts function as traps adsorbing the HC at low temperatures and releases them at higher temperatures whereat the catalytic converter on the vehicle is catalytically active. Reference can be had to assignee's U.S. Pat. No. 6,044,644 issued Apr. 4, 2000 to Hu et al. entitled “Close Coupled Catalyst” for a light-off catalyst and assignee's U.S. Pat. No. 5,804,155 to Farrauto et al. issued Sep. 8, 1998 entitled “Basic Zeolites as Hydrocarbon Traps for Diesel Oxidation Catalysts” for a HC trap in the exhaust system.